Pivoting and lifting structure for sheeting building material

ABSTRACT

The embodiment of the invention disclosed herein is directed to a pivoting and lifting structure for raising building sheet material to a predetermined height, such as, for example, raising dry wall sheets to be fastened to a ceiling. The pivoting and lifting structure includes a platform for receiving a sheet of building material to be raised, this platform including at least one turned edge portion for providing holding means during an initial condition of placing the building sheet material on the platform. As the platform is raised by a simultaneous arcuate and lifting motion the building sheet material is lifted to a desired height. The pivoting and lifting structure also includes a support base upon which the link members of the pivoting and lifting mechanisms are secured. This support base is arranged for easy movement across a floor surface by the provision of wheels placed at four displaced corner positions. The pivoting and lifting mechanism has first and second groups of pivotal arms, each group including at least first, second and third independent pivotal arm members pivotally connected and slidably fastened to one another to effect simultaneous arcuate and raising motion of the support platform means which raises the building sheet material. A cross bar is secured to the first and second groups of pivotal arms and has a central aperture threadedly secured to a threaded shaft, which, in turn, has a journaled end portion fastened to a standard. This standard extends upwardly from a support base. The threaded shaft preferably may be manually operated by a hand crank formed at one end thereof. The support base includes two movable sections, preferably telescopically secured to one another. As the first and second groups of pivotal arms are manipulated by rotation of the threaded shaft the two sections of the support base move relative to one another as a result of drawing in or pushing out of these sections depending on the direction of movement of the pivotal arms.

United States Patent Cordel 1 [11.1 3,822,023 .1451 July 2,1974

[76] Inventor: Ted Cordel, 1101 Williams St.,

Flatwoods, Ky. 41 139 22 Filed: July18, 1973 21 App]. No.: 380,380

Primary Examiner-Frank L. Werner [57] ABSTRACT The embodiment of theinvention disclosed herein is directed to a pivoting and liftingstructure for raising building sheet material to a predetermined height,

such as, for example, raising dry wall sheets to be fasv tened to aceiling. The pivoting and lifting structure includes a platform forreceiving a sheet of building material to be raised, this platformincluding at least one turned edge portion for providing holding meansduring an initial condition of placing the building sheet material onthe platform. As the platform is raised by a simultaneous arcuate andlifting motion the building sheet material is lifted to a desiredheight. The pivoting and lifting structure also includes a support baseupon which the link members of the pivoting and lifting mechanisms aresecured. This support base is arranged for easy movement across a floorsurface by the provision of wheels placed at four displaced comerpositions. The pivoting and lifting mechanism has first and secondgroups of pivotal arms, each group including at least first, second andthird independent pivotal arm members pivotally connected and slidablyfastened to one another to effect simultaneous arcuate and raisingmotion of the support platform means which raises the building sheetmaterial. A cross bar is secured to the first and second groups ofpivotal arms and has a central aperture threadedly secured to a threadedshaft, which, in turn, has a journaled end portion fastened to astandard. This standard extends upwardly from a support base. Thethreaded shaft preferably may be manually operated by a hand crankformed at one end thereof. The support base includes two movablesections, preferably telescopically secured to one another. As the firstand second groups of pivotal arms are manipulated by rotation of thethreaded shaft the two sections of the support base move relative to oneanother as a result of drawing in or pushing out of these sectionsdepending on the direction of movement of the pivotal arms.

10 Claims, 3 Drawing Figures 1 PIVOTING AND LIITING STRUCTURE FORSHEETING BUILDING MATERIAL BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates generally to improvements in structuresand apparatus used primarily in the field of handling buildingmaterials, and more particularly to a pivoting and'lifting structure,and its particular combination of elements, that provide a uniquecooperation of such elements for pivotally and linearly effectingmovement of a platform, which, in turn, raises building sheet materialto a desired height. While the particular structure disclosed herein isdirected primarily to equipment used in the building industry, it willbe understood that this invention is capable of being used in otherallied fields such as warehousing for raising material to be stored inbins and elevated positions, truck and aircraft loading, and the like. i

2. Description of the Prior Art Heretofore, many different types ofstructures have been provided for the building industry to reduce theamount of physical exertion required for raising heavy loads such aswall board or the like to elevations of ceilings for securing suchbuilding materials in place. For example, complicated building boardpositioners have been provided which include mechanisms such as tiltablesupport members secured to linearly actuated ratchet and gear, or whatis sometimes referred to as rack and gear mechanisms, for raising theplatform after it has been placed in a horizontal position. While thistype of structure is effective for the purposes intended, it isrelatively expensive to manufacture and complicated to operate. Forexample a piece of sheet building material is placed on a pivotalsupport and then manually rotated to be in a horizontal position. Thesupport is then locked in place so that it remains in a substantiallyhorizontal position. The linear gear track and ratchet mechanism aremanually operated to effect upward movement of the support plate. Thistype of structure is not only expensive and complicated, but it isrelatively heavy in weight and it therefore is difficult to transportfrom one job site to another.

Another type of prior art structure which can be used for raising sheetbuilding material is one wherein a pipe frame member is arranged toreceive the sheet material and is pivotally secured to a relativelylarge pair of spaced apart standards. The pipe structure is pivotallyrotated by means of cables wrapped about pulleys and block and tacklemeans to effect a mechanical advantage to reduce the amount of physicaleffort required. However this type of structure is extremely complicatedin design and required an exceptional amountof time to manufacture,thereby increasing its ultimate sale cost.

While other types of similar devices have been utilized in a makeshiftmanner to effect substantially the same end result, i.e., that oflifting building sheet material to a desired height, these devices arealso deficient in that they are relatively expensive, complicated and ofheavy construction to be practical for the particular use intended.

SUMMARY OF THE lNVENTlON i Accordingly, this invention is designed toovercome the above noted limitations which are associated with prior artdevices used for raising building sheet material, and will accomplishthis result without detracting from the inherent basic requirements ofsuch devices as safety, portability, and economy of purchase andoperation.

A feature of this invention is the provision of a new and novel pivotingand lifting structure wherein platform means for receiving a buildingsheet material to be raised is positioned initially at a relativelysteep vertical incline. The platform is provided with a lower holdingedge along at least one side thereof to support the sheet of buildingmaterial until it is raised to a substantially horizontal position forsecuring to a ceiling.

Another feature of this invention is the utilization of a pair ofuniquely oriented group of pivotal arms having pivot and slideconnections between the arms to effect simultaneous arcuate and verticalmovement of a support plate upon which a building sheet material isplaced.

Another feature of thisinvention is the provision of a new and novelpivoting and lifting structure wherein the first group of pivotal armshas all of the components and elements thereof substantially in the sameconfiguration and position as the second group of pivotal arms to workin simultaneous conjunction therewith.

Another feature of this invention is the provision of a new and novelpivoting and lifting structure wherein each of the first pivotal arms ofthe first group of pivotal arms is a straight member, and the secondpivotal arm of the first and second groups of pivotal arms is anL-shaped member, and the third pivotal arm of the first and secondgroups of pivotal arms is a straight member, and extending from the endof the first pivotal arm of its respective group. The first and thirdpivotal arms being arranged in such a manner so as to be pivotallysecured at their ends, and the second pivotal arm having one end thereofslidably secured to the third pivotal arm and an intermediate portionthereof slidably secured to the first pivotal arm.

Another features of this invention is the provision of a new and novelpivoting and lifting structure wherein the support base has an openingformed therein, this providing means for the first and second groups ofpivotal arms to extend therethrough and engage the floor surface uponwhich the structure stands.

Another feature of this invention is the provision of a new and novelpivoting and lifting structurwherein roller means are provided at thelower free ends of the second pivotal arms of the first and secondgroups of pivotal arms to allow movement of the first and second groupsof arms over the floor surface upon which the pivoting and liftingstructure is positioned.

Another feature of this invention is the provision of a new and novelpivoting and lifting structure wherein the support base is formed of twosections slidably secured to one another for relative: movement duringturning of a threaded shaft which engages the group of pivoting arms ina manner to effect simultaneous arcuate and vertical movement of theplatform upon which the building sheet material rests.

Another feature of this invention is the provision of a new and novelpivoting and lifting structure wherein an upstanding member extendsupwardly fromone of the two sections of the support base and thethreaded shaft is secured to the standard and extends outwardlytherefrom for manual manipulation to effect a scissorjack action of thetwo groups of pivotal arms for raising the platform.

Another feature of this invention is the provision of a new and novelpivoting and lifting structure wherein the threaded shaft furtherincludes a radially outwardly bent end and axially turned rearwardportion to form a hand crank extending from a journaled portion of theshaft passing through the standard associated with the support base.

Another feature of this invention is the provision of a new and novelpivoting and lifting structure wherein a plurality of wheels areassociated with the support base for easy movement of the structure fromplace to place, at least two of these wheels being equipped with meansfor locking their position relative to the stand so they will notrotate, thereby maintaining the pivoting and lifting structure in agiven position over the floor surface while manipulating the same.

Another feature of this invention is the unique cooperation of elementsso as to operate substantially in a manner similar to that ofa scissorjack, with the exception being that link members are fastened to abottom support plate to effect relative movement of portions of thesupport plate during operation.

Still another feature of this invention is the utilization of a threadedshaft extending from a journaled position of a standard and threadedlyengaging a cross bar associated with the pair of pivotal arm sectionswhereby manual manipulation, as for example by hand crank, can effectsimultaneous arcuate and vertical movement of the platform on which thebuilding sheet material is secured.

Briefly, the pivoting and lifting structure of this invention takesadvantage of a well established and proven lifting technique and appliesit to a new and very practical situation. Original considerations of thedevelopment of this invention called for a lifting unit that can be usedto hold and position large sections of flat or sheet materials to apredetermined height above the floor surface upon which the structurestands. The basic mechanical principles involved are those used in ascissor jack mechanism. Hinged leg sections provide support for thelifting platform, and the lifting force is obtained by means of athreaded shaft or screw member which preferably is manually operated bymeans of a crank section formed at one end thereof. However other meansmay be used to rotate the threaded shaft.

One of the unique and novel features of the present invention residesprimarily in the fact that the lifting platform upon which the buildingsheet material rests does not maintain a constant horizontal positionthroughout the lifting process. In fact, quite a contrary situationexists and the horizontal positon occurs only when the sheet material israised to its predetermined maximum height. When the mechanism is in itslower position, the platform upon which the building sheet material isplaced is positioned slightly offset from the vertical, in a somewhatrather steep inclined vertical position. As the lifting mechanism isenergized as a result of rotating the threaded shaft, the platformslowly changes its positions from an inclined vertical to a horizontalplane, at which time the lifting mechanism is in its full extendedposition.

Many other features and advantages of this invention will be more fullyrealized and understood from the following detailed description whentaken in conjunction with the accompanying drawings wherein likereference numerals through the various views of the drawings areintended to designate similar elements or components.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apivoting and lifting structure constructed in accordance with theprinciples of this invention;

FIG. 2 is a side elevational view showing the pivoting and liftingstructure in its fully vertically extended condition with the platformmember thereof in a horizontal plane to simulate the position of a sheetof building material prior to securing the same to a ceiling or thelike; and

FIG. 3 is a side elevational view of the pivoting and lifting structureof this invention showing the platform in its substantially verticalinclined condition with the pivotal arms of the lifting mechanismoriented in a manner to effect the position as shown.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now to thedrawings, a pivoting and lifting structure for raising building sheetmaterial to a predetermined height over a floor surface is hereillustrated and designated generally by reference numeral 10. Thestructure 10 of this invention includes platform means 12 for receivinga sheet of building material which is to be raised above the floorsurface a predetermined height. The platform means 12 is initiallypositioned at a relatively steep vertical incline, as shown in FIG. 3,so that a sheet of building material can be placed thereon and held inposition by holding means 14. In the illustrated embodiment the platform12 is a single unitary structure of such material as sheet plywood,metal, plastic or the like, and includes a pair of diametrically opposededges which form the holding means 14 when one of the edges is in itslowermost position, as seen in FIG. 3.

The entire pivoting and lifting structure 10 is secured or fabricatedupon a support base 16 which is effectively moved across the floorsurface upon which the entire structure rests by suitable transportmeans, to be described in full detail hereinbelow.

A first group of pivotal arms 18 is positioned near or close to one sideof the support base and a econd group of pivotal arms 20 is positionednear the other side of the support base. The first and second groups ofpivotal arms are arranged substantially parallel to one another and therespective link components thereof are fashioned and arranged inparallel to move in simultaneous relation to one another.

For example, the first group of pivotal arms 18 includes a first pivotalarm 22 which has one free end thereof secured to the support base 16 bymeans of a pivot connection 23. A second pivotal arm 24, hereillustrated as an L-shaped member, has an intermediate slide connection26 movably fastened to the arm 22. One free end of the L-shaped arm 24has a roller or other wheel device 27 secured to the lowermost portionthereof and rolls upon the floor surface through a relatively largeopening 28 formed in the support base. A third pivotal arm 29 has thelower most end portion thereof pivotally secured to the other free endof the pivotal arm 22 and an intermediate portion arranged to 22 securedat 23. Also associated with the second group of pivotal arms 22 is asecond L-shaped pivotal arm 32 which, in turn, has the upper L bracketportion thereof secured to a slide member 33 which slidably engages theupstanding third vertical arm 34. In a like manner, an intermediateportion of the first vertical arm 31 has a slide member 36 to engage theL-shaped pivotal arm 32 substantially centrally thereof. A roller 35 isprovided at the lower end of the arm member 32 similar to that of theroller 27 at the lower end of arm member 24.

The particular arrangement and cooperation of the first and second groupof pivotal arms, 18 and 20, respectively, cooperate in such a manner soas to have the first, second and third pivotal arms associated therewithmoved substantially parallel and simultaneously. To accomplish this across bar section 40 is secured to and extends between the first andsecond groups of pivotal arms to effect this simultaneous pivotaloperation of the two groups of pivotal arms. The cross bar 40 has athreaded aperture, not seen, formed therein and preferably locatedsubstantially centrally of the cross bar. An elongated threaded shaft orscrew 41 is threadedly secured to the threaded aperture and effectsrelative movement of .the two groups of arms as the shaft rotates.

In the illustrated embodiment, the threaded shaft 41 has a journaledportion 42 secured to a standard 43 formed on one portion of the supportbase 16. The journaled portion 42 may be formed by any suitable bearingmeans known in the art, as for example, a brass oil free bearing or aball bearing structure, as desired. Preferably, extending outwardly ofthe threaded shaft 41 is a radially outwardly directed shaft portion 44which is bent and leads into an axially directed hand gripping portion46 which forms the basic components of a hand crank 47. The hand crank47 provides means for effecting manual manipulation of the structureillustrated herein. Rotation of the threaded shaft will cause therespective first, second, and third arms of the first and second groupsof pivotal arms to move relative to one another and effect simultaneousarcuate and vertical lifting movement of the platform 12 so as to liftsheet building material to a predetermined height above the surface ofthe floor on which the structure rests.

The base structure 16 is here illustrated as comprising two sections 48and 49 which are arranged for movement relative to one another. Thisrelative move ment is accomplished by providing telescoping connectionbetween a channel members 50 and 51 which receive correspondingly shapedextension bar sections 52 and 53, respectively. These channels and barsections provide telescoping cooperation with one another to effect thisrelative movement as the threaded shaft 41 is rotated.

in the illustrated embodiment, a pluralityof support wheels 56 arelocated at the various speaced apart corner portions of the structureand arranged so as to have their axis of rotation at right angles to thedirection of relative movement between the. first and second sections 48and 49. The wheels 56 associated with the section 49 include lockingmeans which, in turn, are associated with hand actuating levers 60 and61 to effect manual locking of the wheels. The locking means associatedwith these wheels are associated with the portion of the support basewhich has the standard 43 associated therewith. The other section, i.e.,the section 48, is free to move across the floor surface as the threadedshaft is rotated.

To understand the relative visual operation of the structure illustratedherein, refer particularly to FIG. 3 which shows an initial condition ofthe structure to receivea piece of building sheet material. The sheet material is placed on the platform 12 and is supported by the edge 14. Thehand crank 47 is rotated to provide an arcuate and vertical movement ofthe platform as illustrated by the curved and straight arrowed lines and71, respectively, so tha upon complete manipulation of the structure thepivotal arms are in a position as shown in FIG. 2.

While a single specific embodiment of the present invention has beenillustrated herein, it will be understood that a multitude of differentvariationsa'nd modifications maybe effecting without departing from thespirit and scope of' this invention, as for example, changes to therelative position of the components, size, and material may be effectedwithout departing from the scope of the depending claims. Furthermore,it will be understood that variations as to the building materialforming the structure of this invention may be effected, and suchstructure can be formed of wood, metal, or plastic elements as desired.

Having thus described the invention, what is claimed is: i

1. A pivoting and lifting structure for raising building sheet materialtoa predetermined] height, comprising:

platform means for receiving the building sheet material to be raised,said platform means being initially at a steep vertical incline,

holding means formed along the lowermost edge of said platform meansinitially to support said building sheet material to be raised,

a support base upon which said pivoting and lifting structure issupported over a floor surface,

a first group of pivotal arms pivotally secured together with oneanother, said first group including a first pivotal arm being pivotallysecured to said support base, and a second pivotal arm of said firstgroup extending downwardly below said support base and engaging thefloor surface, and a third pivotal arm of said first group pivotallysecured to said first pivotal arm and slidably fastened to said secondpivotal arm,

a second group of pivotal arms pivotally secured together with oneanother, said second group of pivotal arms including a first pivotal armbeing pivotally secured to said support base, a second pivotal arm ofsaid second group extending downwardly below said support base andengaging the floor surface, and a third pivotal arm of said second groupof arms being pivotally secured to said first pivotal arm and slidablysecured to said! second pivotal arm of said second group,

said first and second groups of pivotal arms being arranged to havetheir respective first, second and third pivotal arm members parallel toone another,

a cross bar secured to and extending between said first and secondgroups of pivotal arms to effect simultaneous pivotal and slidingmovement of said first and second groups of pivotal arms,

a standard extending upwardly from said support base, and

a threaded shaft having a journaled portion rotatively secured to saidstandard and a threaded shaft portion extending from said standard andthreadedly engaging a threaded aperture formed in said cross bar,

whereby, rotation of said threaded shaft will cause the respectivefirst, second and third arms of said first and second groups of pivotalarms to move relative to one another and effect simultaneous arcuatelifting movement of said platform means until said platform means is ina horizontal position.

2. In the pivoting and lifting structure as set forth in claim 1 whereinsaid first group of pivotal arms has all of the components and elementsthereof substantially of the same configuration and position as saidsecond group of pivotal arms to work in simultaneous conjunctiontherewith.

3. In the pivoting and lifting structure as set forth in claim 1 whereineach of said first pivotal arms of said first and second groups ofpivotal arms is a straight member, said second pivotal arms of saidfirst and econd groups of said. pivotal arms is an L-shaped member, andsaid third pivotal arms of said first and second groups of pivotal armsis a straight member and extending from the end of said first pivotalarm s its respective group, said first and third pivotal arms beingpivotally secured at their ends and said second pivotal arm having oneend thereof slidably secured to said third pivotal arm and anintermediate portion thereof slidably secured to said first pivotal arm.

4. In the pivoting and lifting structure as set forth in claim 3 whereinsaid support base has an opening formed therein, said first and secondgroups of pivotal arms being located substantially in registry with saidopening when said pivotal arms are arranged to have said holding meansraised fully upwardly in its horizontal position.

5. In a pivoting and lifting structure as set forth in claim 4 furtherincluding a roller means secured to the lower free ends of said secondpivotal arms of said first and second groups of pivotal arms to allowmovement of said first and second groups of pivotal arms over the floorsurface upon which the pivoting and lifting structure is positioned.

6. In the pivoting and lifting structure as set forth in claim 5 whereinsaid support base is formed of two sections slidably secured to oneanother for relative movement during turning of the threaded shaft so asto allow the first and second groups of pivotal arms to be pulledtransversely toward said standard as said platform means is moved fromits substantially vertical inclined position to its horizontal position.

7. In the pivoting and lifting structure as set forth in claim 6 whereinsaid standard is secured to one section of said two sections and saidfirst pivotal arm of said first and second groups of pivotal arms issecured to the outer section of said two sections of said support basethereby providing means for urging said two sections apart and togetheras a esult of rotation of said threaded shaft.

8. In the pivoting and lifting structure as set forth in claim 7 whereinsaid threaded shaft further includes a radially outwardly bent and anaxially turned rearward portion to form a hand crank extending from saidjournaled portion to allow manual manipulation of said threaded shaftfor raising said platform means.

9. In the pivoting and lifting structure as set forth in claim 8 furtherincluding a plurality of wheels secured to said two sections of saidsupport base said wheels having their axes of rotation at right anglesto the direction of relative movement between said two sections to allowrotation of the wheels as the sections are moved toward and away fromone another as a result of rotation of said threaded shaft.

10. In the pivoting and lifting structure as set forth in claim 9further including locking means associated with at least one pair ofsaid wheels to prevent their relative rotation as the other pair ofwheels rolls along the floor surface during operation of said threadedshaft to effect a lifting condition of said platform means.

1. A pivoting and lifting structure for raising building sheet materialto a predetermined height, comprising: platform means for receiving thebuilding sheet material to be raised, said platform means beinginitially at a steep vertical incline, holding means formed along thelowermost edge of said platform means initially to support said buildingsheet material to be raised, a support base upon which said pivoting andlifting structure is supported over a floor surface, a first group ofpivotal arms pivotally secured together with one another, said firstgroup including a first pivotal arm being pivotally secured to saidsupport base, and a second pivotal arm of said first group extendingdownwardly below said support base and engaging the floor surface, and athird pivotal arm of said first group pivotally secured to said firstpivotal arm and slidably fastened to said second pivotal arm, a secondgroup of pivotal arms pivotally secured together with one another, saidsecond group of pivotal arms including a first pivotal arm beingpivotally secured to said support base, a second pivotal arm of saidsecond group extending downwardly below said support base and engagingthe floor surface, and a third pivotal arm of said second group of armsbeing pivotally secured to said first pivotal arm and slidably securedto said second pivotal arm of said second group, said first and secondgroups of pivotal arms being arranged to have their respective first,second and third pivotal arm members parallel to one another, a crossbar secured to and extending between said first and second groups ofpivotal arms to effect simultaneous pivotal and sliding movement of saidfirst and second groups of pivotal arms, a standard extending upwardlyfrom said support base, and a threaded shaft having a journaled portionrotatively secured to said standard and a threaded shaft portionextending from said standard and threadedly engaging a threaded apertureformed in said cross bar, whereby, rotation of said threaded shaft willcause the respective first, second and third arms of said first andsecond groups of pivotal arms to move relative to one another and effectsimultaneous arcuate lifting movement of said platform means until saidplatform means is in a horizontal position.
 2. In the pivoting andlifting structure as set forth in claim 1 wherein said first group ofpivotal arms has all of the components and elements thereofsubstantially of the same configuration and position as said secondgroup of pivotal arms to work in simultaneous conjunction therewith. 3.In the pivoting and lifting structure as set forth in claim 1 whereineach of said first pivotal arms of said first and second groups ofpivotal arms is a straight member, said second pivotal arms of saidfirst and econd groups of said pivotal arms is an L-shaped member, andsaid third pivotal arms of said first and second groups of pivotal armsis a straight member and extending frOm the end of said first pivotalarm os its respective group, said first and third pivotal arms beingpivotally secured at their ends and said second pivotal arm having oneend thereof slidably secured to said third pivotal arm and anintermediate portion thereof slidably secured to said first pivotal arm.4. In the pivoting and lifting structure as set forth in claim 3 whereinsaid support base has an opening formed therein, said first and secondgroups of pivotal arms being located substantially in registry with saidopening when said pivotal arms are arranged to have said holding meansraised fully upwardly in its horizontal position.
 5. In a pivoting andlifting structure as set forth in claim 4 further including a rollermeans secured to the lower free ends of said second pivotal arms of saidfirst and second groups of pivotal arms to allow movement of said firstand second groups of pivotal arms over the floor surface upon which thepivoting and lifting structure is positioned.
 6. In the pivoting andlifting structure as set forth in claim 5 wherein said support base isformed of two sections slidably secured to one another for relativemovement during turning of the threaded shaft so as to allow the firstand second groups of pivotal arms to be pulled transversely toward saidstandard as said platform means is moved from its substantially verticalinclined position to its horizontal position.
 7. In the pivoting andlifting structure as set forth in claim 6 wherein said standard issecured to one section of said two sections and said first pivotal armof said first and second groups of pivotal arms is secured to the outersection of said two sections of said support base thereby providingmeans for urging said two sections apart and together as a esult ofrotation of said threaded shaft.
 8. In the pivoting and liftingstructure as set forth in claim 7 wherein said threaded shaft furtherincludes a radially outwardly bent and an axially turned rearwardportion to form a hand crank extending from said journaled portion toallow manual manipulation of said threaded shaft for raising saidplatform means.
 9. In the pivoting and lifting structure as set forth inclaim 8 further including a plurality of wheels secured to said twosections of said support base said wheels having their axes of rotationat right angles to the direction of relative movement between said twosections to allow rotation of the wheels as the sections are movedtoward and away from one another as a result of rotation of saidthreaded shaft.
 10. In the pivoting and lifting structure as set forthin claim 9 further including locking means associated with at least onepair of said wheels to prevent their relative rotation as the other pairof wheels rolls along the floor surface during operation of saidthreaded shaft to effect a lifting condition of said platform means.